Ethernet exists as a combination of twisted pair cables along with fiber optic versions connecting end systems to networks. Ethernet is standardized in IEEE 802.3 for Local Area Network (LAN) protocols. 802.3 exists in several varieties including 10, 100, 1000 Megabytes per Second (Mbps) with physical interfaces supporting bi-directional traffic, that is, transmit and receive traffic. An important characteristic of 802.3 versions is that only duplex systems are supported by the standard as described in 802.3, clause 56, particularly clause 56.1. Accordingly, uni-directional Ethernet is not supported by 802.3.
Uni-directional Ethernet supports one-way traffic across a single fiber strand. Uni-directional links are useful for applications, such as broadband video services where almost all traffic flow is in one direction. The links conserve bandwidth by enabling the link to be differentially dedicated to transmit and receive interfaces. Also, the number of ports is conserved because the transmit-only and receive-only interfaces act independently.
The advantages of uni-directional Ethernet may be included under 802.3 by disabling the full duplex requirement of the Media Access Controller (MAC) sub layer in the Data Link Layer supporting the Physical Interface in the Open System Interconnection (OSI) Reference Model. Various alternatives solutions have been used to disable the duplex requirement of the MAC devices including (i) designing non-compliant MAC devices; (ii) providing electrical loop-back of transmit signals to the MAC device, and (iii) providing optical loop-back of transmit signals to the MAC. All of the described alternative solutions are of limited practicality, particularly for small form—factor pluggable modules (SFP) used in Ethernet communications. SFPs are compact, hot-pluggable transceivers used for both telecommunication and data communications and are commercially available from a number of companies including Optical Communication Products (OPC), Woodland Hills, Ca; Canary Communications, Morgan Hill, Ca. and others.
The present invention brings the advantages of uni-directional Ethernet traffic to 802.3 LANs for extended communication services requiring only the usage/connection of a single fiber and providing a mechanism to maintain a link up condition on a compliant Ethernet MAC device for any hardware that accepts SFP modules. A feed back loop from a MAC device transmit terminal to its receive terminal includes (i) a controlled SFP socket and (ii) a SFP module engaged with the socket, the module including a splitter and active device to maintain the receive terminal in an uplink condition during transmission thereby simulating full duplex communication for 802.3 LAN communications.